9702

• UCREFRP Catalog Number: 9702
• Author: Petersen, J.H., and C.P. Paukert.
• Title: Development of a bioenergetics model for humpback chub and evaluation of water temperature changes in the Grand Canyon, Colorado River.
• USFW Year: 2005.
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: NO

966
PETERSEN AND PAUKERT
Results from laboratory growth experiments
were also used in the corroboration process. Gor-
man and VanHoosen's (2000) experiments at tem-
peratures different from 24oC were used in corrob-
oration tests. Summer warming during their exper-
iment caused the lower temperature treatment
(12°C) to warm by about 2-3°C midway through
the experiment. Gorman and VanHoosen (2000)
concluded that there was no significant growth dur-
ing the early period (- 12°C; January to mid-June),
but there was positive growth during the later period
(14-15°C; mid-June to mid-September). Based on
these results, we also separated the low-temperature
treatment into two groups, a 13°C period and a 15°C
period, for corroboration. Actual average temper-
atures for these two periods, 13.0°C and 14.8°C,
were used in corroboration testing. Clarkson and
Childs (2000) grew humpback chub for 90 d at 10,
14, and 20°C in the laboratory, and these results
were also used in corroboration analyses.
Model sensitivity was explored in several ways.
We inspected the coefficient of variation (CV =
100 x SD/mean) of parameter values that met test
criteria and examined the correlation coefficients
of those accepted parameter sets. Sensitivity of the
growth rate of juvenile and subadult humpback
chub was examined by simulating growth at var-
ious temperature and food availability values. Ju-
venile (4.0 g) and subadult (115 g) humpback chub
growth was modeled for 30 d at a given temper-
ature (range 5-32°C) and p value (range 0.1-1.0).
Daily growth rates were averaged during this pe-
riod and results were presented in a response sur-
face plot.
Bioenergetic simulations of potential tempera-
ture control device scenarios.-To demonstrate an
application of the bioenergetic model for hump-
back chub in the lower Colorado River, we com-
pared the growth rates and total consumption for
juvenile and subadult humpback chub grown under
three temperature scenarios (Figure 2): (1) pre-
dam temperature conditions, (2) post-dam tem-
perature conditions, and (3) increased temperature
in May through October (TCD scenario). The TCD
scenario corresponded to a potential management
action that might be implemented to increase water
temperature in the lower Colorado River (Figure
2). Pre- and post-dam simulations were conducted
with the p equal to 0.65 (see Table 3). The TCD
scenario was evaluated assuming no increase in
food availability (p = 0.65) and with an increase
in food availability due to temperature change (p
= 0.75). Diet was constant in all simulations and
growth was evaluated over a 1-year period. Diet
30
2s
0
zo
W
1s
E
m in
m
3
z
f Pre-dam tomperaWm
...0 Post-dam temperature
-7- TCD scenario
to
Month
FIGURE 2.-Average monthly water temperatures in
the Grand Canyon (lower Colorado River) before and
after the construction of Glen Canyon Dam and for a
potential temperature management scenario using a tem-
perature control device (TCD). Temperature data are
from U.S. Geological Survey at river mile 61 near the
confluence with the Little Colorado River.
of humpback chub was taken from Valdez and Ryel
(1995; Table 4). Energy densities of prey were
from Cummins and Wuycheck (1971).
Results
Final Parameter Selection, Model Corroboration,
and Sensitivity
Monte Carlo simulations with 10,000 iterations
produced 273 acceptable data sets assuming sati-
ation (p = 1.0) and 316 data sets assuming feeding
in the growth experiment was below satiation (0.0
< p < 1.0). Assuming feeding was below satiation,
the average value of p was 0.62 (N = 316).
When the two model parameter sets for hump-
back chub (i.e., those based on the satiation and
below-satiation assumptions) were fit to field and
laboratory growth, the satiation parameter values
produced consistently higher food availability es-
timates (p) than the below-satiation parameter val-
ues (Table 3). Assuming satiation in the growth
experiment, values of p in the corroboration tests
ranged from 0.61 to 1.27 with an average of 1.02
(Table 3). Assuming fish were eating below sati-
ation, p ranged from 0.34 to 0.81 and averaged
0.66 (Table 3). Values of p derived from laboratory
experiments were somewhat lower than p values
from field data (Table 3). Specific growth rates
ranged from 0.0 to 3.0% per day; higher growth
rates occurred with smaller fish and higher tem-
peratures (Table 3). Based on the lower and more
reasonable p values in this analysis, simulations
in the remainder of this study used parameter val-
TABLE 3.--C
field growth ral
determined. Tw
feeding (p < 1. .
Life sta
Juvenile
Subadul
Average
Minimu
Maximu
a 1, Val,
Childs
ues that were
below satiati(
ment. Parame
for Gila spp.-
ble 5.
As expecte
tures for resp
TABLE 4.-Et
average contrib
in the Grand C.
rentheses) for s
and Ryel 1995,
Wuycheck (197
Prey taxon or c<
Simuliids
Gammarus spp.
Chironomids
Cladophora spp.
Other aquatic inve
Terrestrial invertet